Glass annealing kiln



May 7, 1946. w. N. WHEAT ET AL GLASS ANNEALING KILN Filed Nov. 4, 1942 "M fud' 1/5 4, Mal/awn) ATTORNEY Patented May '7 E946 Zillilflllfi GLLASS ANNEALKNG KILN William Norman Wheat and Reginald Bullock, Smethwicls, Birmingham, England, assignora to @hanoe firothera and lilo. Limited, Smethwiclr, Birmingham, England Application November it, 1942, Serial No. Midfield in Great May 4, 1M2

l cam," (on. 49-46) This invention relates to electrically heated glass annealing lrllns and particularly kilns for annealing optical glass.

The object of the presentv invention is to enable a more uniform temperature to be obtained part of the chamber, the base and cover of the chamber being shaped to present curved guiding surfaces to the air stream produced by the fan, glass supporting means arranged within and spaced from the inner surfaces of the chamber, a vertical air passage extending axially through the glass-supporting means, and legs whereby the said means is supported on the base of the chamber.

The accompanying drawing is a sectional elevation of a glass annealing kiln embodying the invention.

In carrying the invention into effect as shown, we employ a vertical cylindrical chamber a having a removable top cover b, the side, base and removable top cover or this chamber being con structed from flreclay or other suitable refractory material. The inner faces of the side, base and removable top cover are suitably channelled to accommodate electrical heating elements in the form of wires. The chamber a is contained in a metal or other casing 01 and the space between the chamber and casing may be packed with any convenient thermally insulating material as e. Moreover the top cover is is provided at its upper side with thermally insulating material f surrounded by a metal or other walls.

The heating elements c associated with the underside of the cover' b and/or base or the chamhera may be adapted to provide a sumciently greater lleating action than the other heating I elements, to counteract any lack. of uniformity of by superimposed circular trays 2* supported by legs i on the base or the chamber a, l. e trays are so constructed as to provide vertical air passage is throuuh the trays annular passage m between the peripheries of the trays and the inner vertical surface of the chamber a.

In the lower part 01 the chamber a is arranged an electrically driven centrifugal fan n for circulating the air in the chamber, the air stream produced by the fan being caused to flow up the annular passage m and down the axial passage is. To ensure uniformity of flow in all parts of the air stream the base and cover of the chamber a are suitably shaped to present curved guiding surfaces 0 to the stream.

By combining heating elements 0 with the base and cover as well as with the inner vertical surface of the chamber a we are able to obtain the desired uniform temperature within the chamber in a very satisfactory manner.

After the chamber a has been brought to the desired temperature the chamber and its contents are allowed to cool at a rate which can be determined by gradually diminishing the current the top cover b is provided with lifting bolts t.

and to minimise heat loss these bolts are embedded in the insulation 1.

Whilst it is preferable to employ a cylindrical chamber, this is not essential, as the chamber may be of rectangular, or polygonal form.

Having thus described our invention what we claim as new and desire to secure by Letters Pat out is:

A glass annealing kiln comprising the combination of a vertical chamber having a removable top cover, heating elements associated with the lateral, upper, and lower interior surfaces of the chamber, an air-circulating fan arranged in the lower part of the chamber, the base and cover of the chamber being shaped to present curved guiding surfaces to the air stream produoed by the fan, glass-supporting means arranged within and spaced from the inner surfaces of the chamber, a vertical air passage extending axially through the glass-supporting means, and legs whereby the said means is sup ported on the base of the chamber. 1

NQN WHEAT. REGENALD EULLQCK. 

